The objective of this research project is to develop practical and useful methods of protecting heart function during and after open-heart surgery. Although the patient is placed on the heart-lung machine during cardiac surgery in order to maintain adequate blood flow throughout his body, it is frequently necessary to interrupt blood flow to the heart itself during the course of the open-heart surgery, in order to allow the surgeon to correct the heart defect itself. In this study we are attempting to define the best and most practical methods of protecting the heart during these periods of blood deprivation. Using experimental animal models, we are studying the function of the heart before and after the interruption of blood flow to the heart. We are also able to examine how the heart functions during the interruptions of blood flow using a mass spectrometer technique and, in addition, we make microscopic observations on the heart tissue itself at the completion of the experiment. We are using a variety of new drugs, chemical agents, and temperature changes in our attempt to find the most effective ways of preserving heart function during the period of blood deprivation to the heart. In addition, we have become increasingly aware of the importance of the first few minutes after the resumption of normal blood flow to the heart, and we are also attempting to define the best methods of resuming blood flow to the blood-deprived heart. After we have demonstrated that a particular technique is both safe and results in improve heart protection, we then carefully adapt the improve technique to our open-heart surgery program.